After seeing the various characters Oda's introduced during the Colosseum, I've been thinking about how they might play a part after the colosseum. With a number of them already having some copmlex backstories, to just abandon them after all is said and done doesn't seem like Oda's style or any other decent mangaka's style, for that matter. So, we'll make the obvious prediction- Luffy wins the colosseum, everyone finds out he's actually Straw Hat, Diamante fails to kill him, we move on. Now, we can't accurately predict what kind of relationship Luffy will have with the other contestants after said colosseum, but can we predict how they'll participate in the rest of the arc? Sure we can! I'll break it down per main contestants, just to smooth things out~
Chinjao: Basically, he hated Garp, took it out on Luffy, Luffy beat him, he got his head back. What will his reaction be? Well, to say that he'll forgive Garp would probably be a long shot, but for him to realize the differences between Garp and his descendants might make him reconsider his hatred for Luffy. So, after said hatred is gone, what happens?
Bartolomeo: A totally different story that we're not even aware of yet, Bartolomeo could be a number of things. Because his intentions aren't as clear yet, he's up to any interpretation.
Cavendish: This guy reminds me soooo much of Duval. Completely different backstories and reasons for hating one of the Straw Hats, but could still be won over with something little.
So, are they new allies or more foes?